A typical form of well construction employs a tubular well casing that extends vertically downward from the surface of the earth. Lateral distribution from the well may be provided by an underground line below the frost level for the particular area. A spool, also known as a pitless adaptor, provides a connecting device between the well casing and the surface, provides seals for the line from the well to the lateral distribution line, and provides the sealed joint for the pump actuator or the pump motor electric lines. For maintenance purposes, the spool must be periodically removed by withdrawal through the well casing.
In the installation of the spool into the well casing, the spool is descended through the tubular well casing until the spool seats against either a protrusion in the well casing or against an area on the wall of the well casing where the well casing narrows. The spool is threadedly engaged with a pipe suspended therefrom, the length of which descends below a fluid table, usually a water table. The seating of the spool puts the spool at a proper depth within the casing to align with the lateral distribution line and to suspend the pipe that extends downward for the fluid table.
A typical spool of the prior art is configured to have two conical sections, the conical sections being joined at the middle of the spool such that the tapered ends of the conical sections are formed on opposite ends of the spool. Though this geometry sufficiently resolves the forces acting upon the spool, predominantly the weight of the suspended pipe, the result is that the spool is cast with a significant vertical dimension and requires use of large machining equipment. The large size of the spool also requires a large amount of material from which the spool is cast.